linux/drivers/tty/serial/arc_uart.c
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   1/*
   2 * ARC On-Chip(fpga) UART Driver
   3 *
   4 * Copyright (C) 2010-2012 Synopsys, Inc. (www.synopsys.com)
   5 *
   6 * This program is free software; you can redistribute it and/or modify
   7 * it under the terms of the GNU General Public License version 2 as
   8 * published by the Free Software Foundation.
   9 *
  10 * vineetg: July 10th 2012
  11 *  -Decoupled the driver from arch/arc
  12 *    +Using platform_get_resource() for irq/membase (thx to bfin_uart.c)
  13 *    +Using early_platform_xxx() for early console (thx to mach-shmobile/xxx)
  14 *
  15 * Vineetg: Aug 21st 2010
  16 *  -Is uart_tx_stopped() not done in tty write path as it has already been
  17 *   taken care of, in serial core
  18 *
  19 * Vineetg: Aug 18th 2010
  20 *  -New Serial Core based ARC UART driver
  21 *  -Derived largely from blackfin driver albiet with some major tweaks
  22 *
  23 * TODO:
  24 *  -check if sysreq works
  25 */
  26
  27#if defined(CONFIG_SERIAL_ARC_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
  28#define SUPPORT_SYSRQ
  29#endif
  30
  31#include <linux/module.h>
  32#include <linux/serial.h>
  33#include <linux/console.h>
  34#include <linux/sysrq.h>
  35#include <linux/platform_device.h>
  36#include <linux/tty.h>
  37#include <linux/tty_flip.h>
  38#include <linux/serial_core.h>
  39#include <linux/io.h>
  40#include <linux/of_irq.h>
  41#include <linux/of_address.h>
  42
  43/*************************************
  44 * ARC UART Hardware Specs
  45 ************************************/
  46#define ARC_UART_TX_FIFO_SIZE  1
  47
  48/*
  49 * UART Register set (this is not a Standards Compliant IP)
  50 * Also each reg is Word aligned, but only 8 bits wide
  51 */
  52#define R_ID0   0
  53#define R_ID1   4
  54#define R_ID2   8
  55#define R_ID3   12
  56#define R_DATA  16
  57#define R_STS   20
  58#define R_BAUDL 24
  59#define R_BAUDH 28
  60
  61/* Bits for UART Status Reg (R/W) */
  62#define RXIENB  0x04    /* Receive Interrupt Enable */
  63#define TXIENB  0x40    /* Transmit Interrupt Enable */
  64
  65#define RXEMPTY 0x20    /* Receive FIFO Empty: No char receivede */
  66#define TXEMPTY 0x80    /* Transmit FIFO Empty, thus char can be written into */
  67
  68#define RXFULL  0x08    /* Receive FIFO full */
  69#define RXFULL1 0x10    /* Receive FIFO has space for 1 char (tot space=4) */
  70
  71#define RXFERR  0x01    /* Frame Error: Stop Bit not detected */
  72#define RXOERR  0x02    /* OverFlow Err: Char recv but RXFULL still set */
  73
  74/* Uart bit fiddling helpers: lowest level */
  75#define RBASE(port, reg)      (port->membase + reg)
  76#define UART_REG_SET(u, r, v) writeb((v), RBASE(u, r))
  77#define UART_REG_GET(u, r)    readb(RBASE(u, r))
  78
  79#define UART_REG_OR(u, r, v)  UART_REG_SET(u, r, UART_REG_GET(u, r) | (v))
  80#define UART_REG_CLR(u, r, v) UART_REG_SET(u, r, UART_REG_GET(u, r) & ~(v))
  81
  82/* Uart bit fiddling helpers: API level */
  83#define UART_SET_DATA(uart, val)   UART_REG_SET(uart, R_DATA, val)
  84#define UART_GET_DATA(uart)        UART_REG_GET(uart, R_DATA)
  85
  86#define UART_SET_BAUDH(uart, val)  UART_REG_SET(uart, R_BAUDH, val)
  87#define UART_SET_BAUDL(uart, val)  UART_REG_SET(uart, R_BAUDL, val)
  88
  89#define UART_CLR_STATUS(uart, val) UART_REG_CLR(uart, R_STS, val)
  90#define UART_GET_STATUS(uart)      UART_REG_GET(uart, R_STS)
  91
  92#define UART_ALL_IRQ_DISABLE(uart) UART_REG_CLR(uart, R_STS, RXIENB|TXIENB)
  93#define UART_RX_IRQ_DISABLE(uart)  UART_REG_CLR(uart, R_STS, RXIENB)
  94#define UART_TX_IRQ_DISABLE(uart)  UART_REG_CLR(uart, R_STS, TXIENB)
  95
  96#define UART_ALL_IRQ_ENABLE(uart)  UART_REG_OR(uart, R_STS, RXIENB|TXIENB)
  97#define UART_RX_IRQ_ENABLE(uart)   UART_REG_OR(uart, R_STS, RXIENB)
  98#define UART_TX_IRQ_ENABLE(uart)   UART_REG_OR(uart, R_STS, TXIENB)
  99
 100#define ARC_SERIAL_DEV_NAME     "ttyARC"
 101
 102struct arc_uart_port {
 103        struct uart_port port;
 104        unsigned long baud;
 105};
 106
 107#define to_arc_port(uport)  container_of(uport, struct arc_uart_port, port)
 108
 109static struct arc_uart_port arc_uart_ports[CONFIG_SERIAL_ARC_NR_PORTS];
 110
 111#ifdef CONFIG_SERIAL_ARC_CONSOLE
 112static struct console arc_console;
 113#endif
 114
 115#define DRIVER_NAME     "arc-uart"
 116
 117static struct uart_driver arc_uart_driver = {
 118        .owner          = THIS_MODULE,
 119        .driver_name    = DRIVER_NAME,
 120        .dev_name       = ARC_SERIAL_DEV_NAME,
 121        .major          = 0,
 122        .minor          = 0,
 123        .nr             = CONFIG_SERIAL_ARC_NR_PORTS,
 124#ifdef CONFIG_SERIAL_ARC_CONSOLE
 125        .cons           = &arc_console,
 126#endif
 127};
 128
 129static void arc_serial_stop_rx(struct uart_port *port)
 130{
 131        UART_RX_IRQ_DISABLE(port);
 132}
 133
 134static void arc_serial_stop_tx(struct uart_port *port)
 135{
 136        while (!(UART_GET_STATUS(port) & TXEMPTY))
 137                cpu_relax();
 138
 139        UART_TX_IRQ_DISABLE(port);
 140}
 141
 142/*
 143 * Return TIOCSER_TEMT when transmitter is not busy.
 144 */
 145static unsigned int arc_serial_tx_empty(struct uart_port *port)
 146{
 147        unsigned int stat;
 148
 149        stat = UART_GET_STATUS(port);
 150        if (stat & TXEMPTY)
 151                return TIOCSER_TEMT;
 152
 153        return 0;
 154}
 155
 156/*
 157 * Driver internal routine, used by both tty(serial core) as well as tx-isr
 158 *  -Called under spinlock in either cases
 159 *  -also tty->stopped has already been checked
 160 *     = by uart_start( ) before calling us
 161 *     = tx_ist checks that too before calling
 162 */
 163static void arc_serial_tx_chars(struct uart_port *port)
 164{
 165        struct circ_buf *xmit = &port->state->xmit;
 166        int sent = 0;
 167        unsigned char ch;
 168
 169        if (unlikely(port->x_char)) {
 170                UART_SET_DATA(port, port->x_char);
 171                port->icount.tx++;
 172                port->x_char = 0;
 173                sent = 1;
 174        } else if (!uart_circ_empty(xmit)) {
 175                ch = xmit->buf[xmit->tail];
 176                xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
 177                port->icount.tx++;
 178                while (!(UART_GET_STATUS(port) & TXEMPTY))
 179                        cpu_relax();
 180                UART_SET_DATA(port, ch);
 181                sent = 1;
 182        }
 183
 184        /*
 185         * If num chars in xmit buffer are too few, ask tty layer for more.
 186         * By Hard ISR to schedule processing in software interrupt part
 187         */
 188        if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
 189                uart_write_wakeup(port);
 190
 191        if (sent)
 192                UART_TX_IRQ_ENABLE(port);
 193}
 194
 195/*
 196 * port is locked and interrupts are disabled
 197 * uart_start( ) calls us under the port spinlock irqsave
 198 */
 199static void arc_serial_start_tx(struct uart_port *port)
 200{
 201        arc_serial_tx_chars(port);
 202}
 203
 204static void arc_serial_rx_chars(struct uart_port *port, unsigned int status)
 205{
 206        unsigned int ch, flg = 0;
 207
 208        /*
 209         * UART has 4 deep RX-FIFO. Driver's recongnition of this fact
 210         * is very subtle. Here's how ...
 211         * Upon getting a RX-Intr, such that RX-EMPTY=0, meaning data available,
 212         * driver reads the DATA Reg and keeps doing that in a loop, until
 213         * RX-EMPTY=1. Multiple chars being avail, with a single Interrupt,
 214         * before RX-EMPTY=0, implies some sort of buffering going on in the
 215         * controller, which is indeed the Rx-FIFO.
 216         */
 217        do {
 218                /*
 219                 * This could be an Rx Intr for err (no data),
 220                 * so check err and clear that Intr first
 221                 */
 222                if (unlikely(status & (RXOERR | RXFERR))) {
 223                        if (status & RXOERR) {
 224                                port->icount.overrun++;
 225                                flg = TTY_OVERRUN;
 226                                UART_CLR_STATUS(port, RXOERR);
 227                        }
 228
 229                        if (status & RXFERR) {
 230                                port->icount.frame++;
 231                                flg = TTY_FRAME;
 232                                UART_CLR_STATUS(port, RXFERR);
 233                        }
 234                } else
 235                        flg = TTY_NORMAL;
 236
 237                if (status & RXEMPTY)
 238                        continue;
 239
 240                ch = UART_GET_DATA(port);
 241                port->icount.rx++;
 242
 243                if (!(uart_handle_sysrq_char(port, ch)))
 244                        uart_insert_char(port, status, RXOERR, ch, flg);
 245
 246                spin_unlock(&port->lock);
 247                tty_flip_buffer_push(&port->state->port);
 248                spin_lock(&port->lock);
 249        } while (!((status = UART_GET_STATUS(port)) & RXEMPTY));
 250}
 251
 252/*
 253 * A note on the Interrupt handling state machine of this driver
 254 *
 255 * kernel printk writes funnel thru the console driver framework and in order
 256 * to keep things simple as well as efficient, it writes to UART in polled
 257 * mode, in one shot, and exits.
 258 *
 259 * OTOH, Userland output (via tty layer), uses interrupt based writes as there
 260 * can be undeterministic delay between char writes.
 261 *
 262 * Thus Rx-interrupts are always enabled, while tx-interrupts are by default
 263 * disabled.
 264 *
 265 * When tty has some data to send out, serial core calls driver's start_tx
 266 * which
 267 *   -checks-if-tty-buffer-has-char-to-send
 268 *   -writes-data-to-uart
 269 *   -enable-tx-intr
 270 *
 271 * Once data bits are pushed out, controller raises the Tx-room-avail-Interrupt.
 272 * The first thing Tx ISR does is disable further Tx interrupts (as this could
 273 * be the last char to send, before settling down into the quiet polled mode).
 274 * It then calls the exact routine used by tty layer write to send out any
 275 * more char in tty buffer. In case of sending, it re-enables Tx-intr. In case
 276 * of no data, it remains disabled.
 277 * This is how the transmit state machine is dynamically switched on/off
 278 */
 279
 280static irqreturn_t arc_serial_isr(int irq, void *dev_id)
 281{
 282        struct uart_port *port = dev_id;
 283        unsigned int status;
 284
 285        status = UART_GET_STATUS(port);
 286
 287        /*
 288         * Single IRQ for both Rx (data available) Tx (room available) Interrupt
 289         * notifications from the UART Controller.
 290         * To demultiplex between the two, we check the relevant bits
 291         */
 292        if (status & RXIENB) {
 293
 294                /* already in ISR, no need of xx_irqsave */
 295                spin_lock(&port->lock);
 296                arc_serial_rx_chars(port, status);
 297                spin_unlock(&port->lock);
 298        }
 299
 300        if ((status & TXIENB) && (status & TXEMPTY)) {
 301
 302                /* Unconditionally disable further Tx-Interrupts.
 303                 * will be enabled by tx_chars() if needed.
 304                 */
 305                UART_TX_IRQ_DISABLE(port);
 306
 307                spin_lock(&port->lock);
 308
 309                if (!uart_tx_stopped(port))
 310                        arc_serial_tx_chars(port);
 311
 312                spin_unlock(&port->lock);
 313        }
 314
 315        return IRQ_HANDLED;
 316}
 317
 318static unsigned int arc_serial_get_mctrl(struct uart_port *port)
 319{
 320        /*
 321         * Pretend we have a Modem status reg and following bits are
 322         *  always set, to satify the serial core state machine
 323         *  (DSR) Data Set Ready
 324         *  (CTS) Clear To Send
 325         *  (CAR) Carrier Detect
 326         */
 327        return TIOCM_CTS | TIOCM_DSR | TIOCM_CAR;
 328}
 329
 330static void arc_serial_set_mctrl(struct uart_port *port, unsigned int mctrl)
 331{
 332        /* MCR not present */
 333}
 334
 335static void arc_serial_break_ctl(struct uart_port *port, int break_state)
 336{
 337        /* ARC UART doesn't support sending Break signal */
 338}
 339
 340static int arc_serial_startup(struct uart_port *port)
 341{
 342        /* Before we hook up the ISR, Disable all UART Interrupts */
 343        UART_ALL_IRQ_DISABLE(port);
 344
 345        if (request_irq(port->irq, arc_serial_isr, 0, "arc uart rx-tx", port)) {
 346                dev_warn(port->dev, "Unable to attach ARC UART intr\n");
 347                return -EBUSY;
 348        }
 349
 350        UART_RX_IRQ_ENABLE(port); /* Only Rx IRQ enabled to begin with */
 351
 352        return 0;
 353}
 354
 355/* This is not really needed */
 356static void arc_serial_shutdown(struct uart_port *port)
 357{
 358        free_irq(port->irq, port);
 359}
 360
 361static void
 362arc_serial_set_termios(struct uart_port *port, struct ktermios *new,
 363                       struct ktermios *old)
 364{
 365        struct arc_uart_port *uart = to_arc_port(port);
 366        unsigned int baud, uartl, uarth, hw_val;
 367        unsigned long flags;
 368
 369        /*
 370         * Use the generic handler so that any specially encoded baud rates
 371         * such as SPD_xx flags or "%B0" can be handled
 372         * Max Baud I suppose will not be more than current 115K * 4
 373         * Formula for ARC UART is: hw-val = ((CLK/(BAUD*4)) -1)
 374         * spread over two 8-bit registers
 375         */
 376        baud = uart_get_baud_rate(port, new, old, 0, 460800);
 377
 378        hw_val = port->uartclk / (uart->baud * 4) - 1;
 379        uartl = hw_val & 0xFF;
 380        uarth = (hw_val >> 8) & 0xFF;
 381
 382        spin_lock_irqsave(&port->lock, flags);
 383
 384        UART_ALL_IRQ_DISABLE(port);
 385
 386        UART_SET_BAUDL(port, uartl);
 387        UART_SET_BAUDH(port, uarth);
 388
 389        UART_RX_IRQ_ENABLE(port);
 390
 391        /*
 392         * UART doesn't support Parity/Hardware Flow Control;
 393         * Only supports 8N1 character size
 394         */
 395        new->c_cflag &= ~(CMSPAR|CRTSCTS|CSIZE);
 396        new->c_cflag |= CS8;
 397
 398        if (old)
 399                tty_termios_copy_hw(new, old);
 400
 401        /* Don't rewrite B0 */
 402        if (tty_termios_baud_rate(new))
 403                tty_termios_encode_baud_rate(new, baud, baud);
 404
 405        uart_update_timeout(port, new->c_cflag, baud);
 406
 407        spin_unlock_irqrestore(&port->lock, flags);
 408}
 409
 410static const char *arc_serial_type(struct uart_port *port)
 411{
 412        return port->type == PORT_ARC ? DRIVER_NAME : NULL;
 413}
 414
 415static void arc_serial_release_port(struct uart_port *port)
 416{
 417}
 418
 419static int arc_serial_request_port(struct uart_port *port)
 420{
 421        return 0;
 422}
 423
 424/*
 425 * Verify the new serial_struct (for TIOCSSERIAL).
 426 */
 427static int
 428arc_serial_verify_port(struct uart_port *port, struct serial_struct *ser)
 429{
 430        if (port->type != PORT_UNKNOWN && ser->type != PORT_ARC)
 431                return -EINVAL;
 432
 433        return 0;
 434}
 435
 436/*
 437 * Configure/autoconfigure the port.
 438 */
 439static void arc_serial_config_port(struct uart_port *port, int flags)
 440{
 441        if (flags & UART_CONFIG_TYPE)
 442                port->type = PORT_ARC;
 443}
 444
 445#ifdef CONFIG_CONSOLE_POLL
 446
 447static void arc_serial_poll_putchar(struct uart_port *port, unsigned char chr)
 448{
 449        while (!(UART_GET_STATUS(port) & TXEMPTY))
 450                cpu_relax();
 451
 452        UART_SET_DATA(port, chr);
 453}
 454
 455static int arc_serial_poll_getchar(struct uart_port *port)
 456{
 457        unsigned char chr;
 458
 459        while (!(UART_GET_STATUS(port) & RXEMPTY))
 460                cpu_relax();
 461
 462        chr = UART_GET_DATA(port);
 463        return chr;
 464}
 465#endif
 466
 467static struct uart_ops arc_serial_pops = {
 468        .tx_empty       = arc_serial_tx_empty,
 469        .set_mctrl      = arc_serial_set_mctrl,
 470        .get_mctrl      = arc_serial_get_mctrl,
 471        .stop_tx        = arc_serial_stop_tx,
 472        .start_tx       = arc_serial_start_tx,
 473        .stop_rx        = arc_serial_stop_rx,
 474        .break_ctl      = arc_serial_break_ctl,
 475        .startup        = arc_serial_startup,
 476        .shutdown       = arc_serial_shutdown,
 477        .set_termios    = arc_serial_set_termios,
 478        .type           = arc_serial_type,
 479        .release_port   = arc_serial_release_port,
 480        .request_port   = arc_serial_request_port,
 481        .config_port    = arc_serial_config_port,
 482        .verify_port    = arc_serial_verify_port,
 483#ifdef CONFIG_CONSOLE_POLL
 484        .poll_put_char = arc_serial_poll_putchar,
 485        .poll_get_char = arc_serial_poll_getchar,
 486#endif
 487};
 488
 489#ifdef CONFIG_SERIAL_ARC_CONSOLE
 490
 491static int arc_serial_console_setup(struct console *co, char *options)
 492{
 493        struct uart_port *port;
 494        int baud = 115200;
 495        int bits = 8;
 496        int parity = 'n';
 497        int flow = 'n';
 498
 499        if (co->index < 0 || co->index >= CONFIG_SERIAL_ARC_NR_PORTS)
 500                return -ENODEV;
 501
 502        /*
 503         * The uart port backing the console (e.g. ttyARC1) might not have been
 504         * init yet. If so, defer the console setup to after the port.
 505         */
 506        port = &arc_uart_ports[co->index].port;
 507        if (!port->membase)
 508                return -ENODEV;
 509
 510        if (options)
 511                uart_parse_options(options, &baud, &parity, &bits, &flow);
 512
 513        /*
 514         * Serial core will call port->ops->set_termios( )
 515         * which will set the baud reg
 516         */
 517        return uart_set_options(port, co, baud, parity, bits, flow);
 518}
 519
 520static void arc_serial_console_putchar(struct uart_port *port, int ch)
 521{
 522        while (!(UART_GET_STATUS(port) & TXEMPTY))
 523                cpu_relax();
 524
 525        UART_SET_DATA(port, (unsigned char)ch);
 526}
 527
 528/*
 529 * Interrupts are disabled on entering
 530 */
 531static void arc_serial_console_write(struct console *co, const char *s,
 532                                     unsigned int count)
 533{
 534        struct uart_port *port = &arc_uart_ports[co->index].port;
 535        unsigned long flags;
 536
 537        spin_lock_irqsave(&port->lock, flags);
 538        uart_console_write(port, s, count, arc_serial_console_putchar);
 539        spin_unlock_irqrestore(&port->lock, flags);
 540}
 541
 542static struct console arc_console = {
 543        .name   = ARC_SERIAL_DEV_NAME,
 544        .write  = arc_serial_console_write,
 545        .device = uart_console_device,
 546        .setup  = arc_serial_console_setup,
 547        .flags  = CON_PRINTBUFFER,
 548        .index  = -1,
 549        .data   = &arc_uart_driver
 550};
 551
 552static __init void arc_early_serial_write(struct console *con, const char *s,
 553                                          unsigned int n)
 554{
 555        struct earlycon_device *dev = con->data;
 556
 557        uart_console_write(&dev->port, s, n, arc_serial_console_putchar);
 558}
 559
 560static int __init arc_early_console_setup(struct earlycon_device *dev,
 561                                          const char *opt)
 562{
 563        struct uart_port *port = &dev->port;
 564        unsigned int l, h, hw_val;
 565
 566        if (!dev->port.membase)
 567                return -ENODEV;
 568
 569        hw_val = port->uartclk / (dev->baud * 4) - 1;
 570        l = hw_val & 0xFF;
 571        h = (hw_val >> 8) & 0xFF;
 572
 573        UART_SET_BAUDL(port, l);
 574        UART_SET_BAUDH(port, h);
 575
 576        dev->con->write = arc_early_serial_write;
 577        return 0;
 578}
 579OF_EARLYCON_DECLARE(arc_uart, "snps,arc-uart", arc_early_console_setup);
 580
 581#endif  /* CONFIG_SERIAL_ARC_CONSOLE */
 582
 583static int arc_serial_probe(struct platform_device *pdev)
 584{
 585        struct device_node *np = pdev->dev.of_node;
 586        struct arc_uart_port *uart;
 587        struct uart_port *port;
 588        int dev_id;
 589        u32 val;
 590
 591        /* no device tree device */
 592        if (!np)
 593                return -ENODEV;
 594
 595        dev_id = of_alias_get_id(np, "serial");
 596        if (dev_id < 0)
 597                dev_id = 0;
 598
 599        uart = &arc_uart_ports[dev_id];
 600        port = &uart->port;
 601
 602        if (of_property_read_u32(np, "clock-frequency", &val)) {
 603                dev_err(&pdev->dev, "clock-frequency property NOTset\n");
 604                return -EINVAL;
 605        }
 606        port->uartclk = val;
 607
 608        if (of_property_read_u32(np, "current-speed", &val)) {
 609                dev_err(&pdev->dev, "current-speed property NOT set\n");
 610                return -EINVAL;
 611        }
 612        uart->baud = val;
 613
 614        port->membase = of_iomap(np, 0);
 615        if (!port->membase)
 616                /* No point of dev_err since UART itself is hosed here */
 617                return -ENXIO;
 618
 619        port->irq = irq_of_parse_and_map(np, 0);
 620
 621        port->dev = &pdev->dev;
 622        port->iotype = UPIO_MEM;
 623        port->flags = UPF_BOOT_AUTOCONF;
 624        port->line = dev_id;
 625        port->ops = &arc_serial_pops;
 626
 627        port->fifosize = ARC_UART_TX_FIFO_SIZE;
 628
 629        /*
 630         * uart_insert_char( ) uses it in decideding whether to ignore a
 631         * char or not. Explicitly setting it here, removes the subtelty
 632         */
 633        port->ignore_status_mask = 0;
 634
 635        return uart_add_one_port(&arc_uart_driver, &arc_uart_ports[dev_id].port);
 636}
 637
 638static int arc_serial_remove(struct platform_device *pdev)
 639{
 640        /* This will never be called */
 641        return 0;
 642}
 643
 644static const struct of_device_id arc_uart_dt_ids[] = {
 645        { .compatible = "snps,arc-uart" },
 646        { /* Sentinel */ }
 647};
 648MODULE_DEVICE_TABLE(of, arc_uart_dt_ids);
 649
 650static struct platform_driver arc_platform_driver = {
 651        .probe = arc_serial_probe,
 652        .remove = arc_serial_remove,
 653        .driver = {
 654                .name = DRIVER_NAME,
 655                .of_match_table  = arc_uart_dt_ids,
 656         },
 657};
 658
 659static int __init arc_serial_init(void)
 660{
 661        int ret;
 662
 663        ret = uart_register_driver(&arc_uart_driver);
 664        if (ret)
 665                return ret;
 666
 667        ret = platform_driver_register(&arc_platform_driver);
 668        if (ret)
 669                uart_unregister_driver(&arc_uart_driver);
 670
 671        return ret;
 672}
 673
 674static void __exit arc_serial_exit(void)
 675{
 676        platform_driver_unregister(&arc_platform_driver);
 677        uart_unregister_driver(&arc_uart_driver);
 678}
 679
 680module_init(arc_serial_init);
 681module_exit(arc_serial_exit);
 682
 683MODULE_LICENSE("GPL");
 684MODULE_ALIAS("platform:" DRIVER_NAME);
 685MODULE_AUTHOR("Vineet Gupta");
 686MODULE_DESCRIPTION("ARC(Synopsys) On-Chip(fpga) serial driver");
 687